System And Method Of Controlling A Variable-Capacity Compressor And A Variable-Capacity Fan Using A Two-Stage Thermostat

ABSTRACT

A system includes a compressor, an indoor fan, a thermostat, an indoor fan controller, and a compressor controller. The thermostat provides first and second signals based on indoor loading. The fan controller operates the fan in low speed mode and the compressor controller operates the compressor in low capacity mode when only the first signal is asserted. The compressor controller automatically switches the compressor to high capacity mode if only the first signal remains asserted past the low capacity mode runtime. The fan controller operates the fan in high speed mode when the second signal is asserted while the first signal is still asserted. The compressor controller continues to operate the compressor in high capacity mode and the fan controller operates the fan in low speed mode after the second signal is de-asserted, until the first signal is de-asserted, at which point the fan and compressor are turned off.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/309,048, filed on Mar. 16, 2016. The entire disclosure of the aboveapplication is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to two-stage a climate-control systemshaving a variable-capacity compressor and a two-stage thermostat and tomethods for controlling the climate-control system.

BACKGROUND

This section provides background information related to the presentdisclosure and is not necessarily prior art.

A climate-control system such as, for example, a heat-pump system, arefrigeration system, or an air conditioning system, may include a fluidcircuit having an outdoor heat exchanger, an indoor heat exchanger, anexpansion device disposed between the indoor and outdoor heatexchangers, and a compressor circulating a working fluid (e.g.,refrigerant or carbon dioxide) between the indoor and outdoor heatexchangers. Varying a capacity of the compressor can impact theenergy-efficiency of the system and the speed with which the system isable to heat or cool a room or space.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one form, a climate control system comprises a two stage thermostat,a compressor, an indoor fan, and a controller. The two stage thermostatprovides a first signal based on detecting a first condition relating toan indoor temperature and a second signal based on detecting a secondcondition relating to the indoor temperature. The compressor is operableat a first capacity and a second capacity that is greater than the firstcapacity based on one or more of the first signal and the second signal.The indoor fan is operable at a first speed and a second speed that isgreater than the first speed based on one or more of the first signaland the second signal. The controller operates the compressor and thefan as follows. In response to the two stage thermostat asserting thefirst signal, the controller operates the compressor and the faninitially at the first capacity and the first speed and subsequently atthe second capacity and the first speed. Thereafter, in response to thetwo stage thermostat asserting the second signal, the controlleroperates the compressor and the fan at the second capacity and thesecond speed. Thereafter, in response to the two stage thermostatde-asserting the second signal, the controller operates the compressorand the fan at the second capacity and the first speed until the firstsignal is de-asserted.

In some configurations, the two stage thermostat detects the firstcondition when the indoor temperature differs from a desired temperaturesetting of the two stage thermostat by a first amount. The two stagethermostat detects the second condition when the indoor temperaturediffers from the desired temperature setting of the two stage thermostatby a second amount.

In some configurations, the controller operates the compressor and thefan, in response to the two stage thermostat asserting the first signal,initially at the first capacity and the first speed for a predeterminedtime period and subsequently at the second capacity and the first speedbased on an outdoor air temperature or other measured indicator ofoutdoor thermal load.

In some configurations, the two stage thermostat asserts the secondsignal in response to the indoor temperature differing from a desiredtemperature by greater than or equal to a predetermined amount after thecompressor and the indoor fan have been operated respectively at thesecond capacity and the first speed for a predetermined time period.

In some configurations, the two stage thermostat asserts the secondsignal after the compressor and the indoor fan have been operatedrespectively at the second capacity and the first speed for apredetermined time period.

In some configurations, the two stage thermostat asserts the secondsignal for a predetermined time period and de-asserts the second signalafter the predetermined time period.

In some configurations, the two stage thermostat asserts the secondsignal until the indoor temperature differs from a desired temperatureby less than or equal to a predetermined amount and de-asserts thesecond signal after the indoor temperature differs from the desiredtemperature by less than or equal to the predetermined amount.

In some configurations, the controller turns off the compressor and thefan after the first signal is de-asserted.

In another form, a control system comprises a thermostat, a compressor,an indoor fan, and a controller. The thermostat provides a first signalin response to detecting a first demand for changing an indoortemperature by a first amount and a second signal in response todetecting a second demand for changing the indoor temperature by asecond amount. The compressor is operable at a first capacity and asecond capacity that is greater than the first capacity. The indoor fanis operable at a first speed and a second speed that is greater than thefirst speed. The controller operates the compressor and the fan asfollows. In response to the thermostat asserting the first signal, thecontroller operates the compressor and the fan initially at the firstcapacity and the first speed and subsequently at the second capacity andthe first speed. Then in response to the thermostat asserting the secondsignal, the controller operates the compressor and the fan at the secondcapacity and the second speed. Then in response to the thermostatde-asserting the second signal, the controller operates the compressorand the fan at the second capacity and the first speed until the firstsignal is de-asserted.

In some configurations, the thermostat detects the first demand when theindoor temperature differs from a desired temperature setting of thethermostat by the first amount. The thermostat detects the second demandwhen the indoor temperature differs from the desired temperature settingof the thermostat by the second amount.

In some configurations, the controller operates the compressor and thefan, in response to the thermostat asserting the first signal, initiallyat the first capacity and the first speed for a predetermined timeperiod and subsequently at the second capacity and the first speed basedon an outdoor air temperature or other measured indicator of outdoorthermal load.

In some configurations, the thermostat asserts the second signal inresponse to the indoor temperature differing from a desired temperatureby greater than or equal to a predetermined amount after the compressorand the indoor fan have been operated respectively at the secondcapacity and the first speed for a predetermined time period.

In some configurations, the thermostat asserts the second signal afterthe compressor and the indoor fan have been operated respectively at thesecond capacity and the first speed for a predetermined time period.

In some configurations, the thermostat asserts the second signal for apredetermined time period de-asserts the second signal after thepredetermined time period.

In some configurations, the thermostat asserts the second signal untilthe indoor temperature differs from a desired temperature by less thanor equal to a predetermined amount and de-asserts the second signalafter the indoor temperature differs from the desired temperature byless than or equal to the predetermined amount.

In some configurations, the controller turns off the compressor and thefan after the first signal is de-asserted.

In another form, a system comprises a compressor, an indoor fan, athermostat, and a controller. The compressor is operable at a firstcapacity and a second capacity that is greater than the first capacity.The indoor fan is operable at a first speed and a second speed that isgreater than the first speed. The thermostat provides a first signal forchanging an indoor temperature by a first amount and a second signal forchanging the indoor temperature by a second amount. The controlleroperates the compressor and the fan as follows. In response to thethermostat asserting the first signal, the controller operates thecompressor and the fan initially at the first capacity and the firstspeed and subsequently at the second capacity and the first speed. Thenin response to the thermostat asserting the second signal, thecontroller operates the compressor and the fan at the second capacityand the second speed until the second signal is de-asserted. Then thecontroller operates the compressor and the fan at the second capacityand the first speed until the first signal is de-asserted.

In some configurations, the controller operates the compressor and thefan, in response to the thermostat asserting the first signal, initiallyat the first capacity and the first speed for a predetermined timeperiod and subsequently at the second capacity and the first speed basedon an outdoor air temperature or other measured indicator of outdoorthermal load.

In some configurations, the thermostat asserts the second signal inresponse to the indoor temperature differing from a desired temperatureby greater than or equal to a predetermined amount after the compressorand the indoor fan have been operated respectively at the secondcapacity and the first speed for a predetermined time period.

In some configurations, the thermostat asserts the second signal afterthe compressor and the indoor fan have been operated respectively at thesecond capacity and the first speed for a predetermined time period.

In some configurations, the thermostat asserts the second signal for apredetermined time period and de-asserts the second signal after thepredetermined time period.

In some configurations, the thermostat asserts the second signal untilthe indoor temperature differs from a desired temperature by less thanor equal to a predetermined amount and de-asserts the second signalafter the indoor temperature differs from the desired temperature byless than or equal to the predetermined amount.

In some configurations, the controller turns off the compressor and thefan after the first signal is de-asserted.

In another form, a system comprises a compressor, an indoor fan, athermostat, and a controller. The compressor is operable at a firstcapacity and a second capacity that is greater than the first capacity.The indoor fan is operable at a first speed and a second speed that isgreater than the first speed. The thermostat provides a first signal forchanging an indoor temperature by a first amount and a second signal forchanging the indoor temperature by a second amount. The controlleroperates the compressor and the fan at the second capacity and thesecond speed in response to the thermostat asserting the second signaland _([AJV[1])asserting the first signal. Subsequently, the controlleroperates the compressor and the fan at the second capacity and the firstspeed in response to the thermostat de-asserting the second signal andasserting the first signal.

In some configurations, the controller operates the compressor and thefan at the second capacity and the first speed until the first signal isde-asserted and turns off the compressor and the fan after the firstsignal is de-asserted.

In some configurations, the controller operates the compressor and thefan at the second capacity and the first speed based on an outdoor airtemperature or other measured indicator of outdoor thermal load.

In another form, a method for a compressor operable at a first capacityand a second capacity that is greater than the first capacity and anindoor fan operable at a first speed and a second speed that is greaterthan the first speed, comprises providing a first signal in response todetecting a first demand for changing an indoor temperature by a firstamount and a second signal in response to detecting a second demand forchanging the indoor temperature by a second amount. The method furthercomprises in response to the first signal being asserted, operating thecompressor and the fan initially at the first capacity and the firstspeed and subsequently at the second capacity and the first speed, thenin response to the second signal being asserted, operating thecompressor and the fan at the second capacity and the second speed, andthen in response to the second signal being de-asserted, operating thecompressor and the fan at the second capacity and the first speed untilthe first signal is de-asserted.

In some configurations, the method further comprises operating thecompressor and the fan, in response to the first signal being asserted,initially at the first capacity and the first speed for a predeterminedtime period and subsequently at the second capacity and the first speedbased on an outdoor air temperature or other measured indicator ofoutdoor thermal load.

In some configurations, the method further comprises asserting thesecond signal in response to the indoor temperature differing from adesired temperature by greater than or equal to a predetermined amountafter the compressor and the indoor fan have been operated respectivelyat the second capacity and the first speed for a predetermined timeperiod.

In some configurations, the method further comprises asserting thesecond signal after the compressor and the indoor fan have been operatedrespectively at the second capacity and the first speed for apredetermined time period.

In some configurations, the method further comprises asserting thesecond signal for a predetermined time period and de-asserting thesecond signal after the predetermined time period.

In some configurations, the method further comprises asserting thesecond signal until the indoor temperature differs from a desiredtemperature by less than or equal to a predetermined amount, andde-asserting the second signal after the indoor temperature differs fromthe desired temperature by less than or equal to the predeterminedamount.

In some configurations, the method further comprises turning off thecompressor and the fan after the first signal is de-asserted.

In another form, a method for a compressor operable at a first capacityand a second capacity that is greater than the first capacity and anindoor fan operable at a first speed and a second speed that is greaterthan the first speed, comprises providing a first signal for changing anindoor temperature by a first amount and a second signal for changingthe indoor temperature by a second amount. The method further comprisesoperating the compressor and the fan at the second capacity and thesecond speed in response to the second signal being asserted and thefirst signal _([AJV[2])being asserted. The method further comprisessubsequently operating the compressor and the fan at the second capacityand the first speed in response to the second signal being de-assertingand the first signal being asserted.

In some configurations, the method further comprises operating thecompressor and the fan at the second capacity and the first speed untilthe first signal is de-asserted, and turning off the compressor and thefan after the first signal is de-asserted.

In some configurations, the method further comprises operating thecompressor and the fan at the second capacity and the first speed basedon an outdoor air temperature or other measured indicator of outdoorthermal load.

In another form, a system comprises a compressor, an indoor fan, athermostat, and a controller. The compressor is operable at a firstcapacity and a second capacity that is greater than the first capacity.The indoor fan is operable at a first speed and a second speed that isgreater than the first speed. The thermostat provides a first signal forchanging an indoor temperature by a first amount and a second signal forchanging the indoor temperature by a second amount. The controlleroperates the compressor and the fan at the second capacity and thesecond speed in response to the thermostat asserting the first signaland the second signal, and in response to an outdoor air temperature orother measured indicator of outdoor thermal load being greater than orequal to a predetermined threshold. Subsequently, the controlleroperates the compressor and the fan at the second capacity and the firstspeed in response to the thermostat de-asserting the second signal whilethe first signal remains asserted.

In some configurations, the controller operates the compressor and thefan at the second capacity and the first speed until the first signal isde-asserted and turns off the compressor and the fan after the firstsignal is de-asserted.

In another form, a method for a compressor operable at a first capacityand a second capacity that is greater than the first capacity and anindoor fan operable at a first speed and a second speed that is greaterthan the first speed, comprises providing a first signal for changing anindoor temperature by a first amount and a second signal for changingthe indoor temperature by a second amount. The method further comprisesoperating the compressor and the fan at the second capacity and thesecond speed in response to the first signal and the second signal beingasserted, and in response to an outdoor air temperature or othermeasured indicator of outdoor thermal load being greater than or equalto a predetermined threshold. The method further comprises subsequentlyoperating the compressor and the fan at the second capacity and thefirst speed in response to the second signal being de-asserted while thefirst signal remains asserted.

In some configurations, the method further comprises operating thecompressor and the fan at the second capacity and the first speed untilthe first signal is de-asserted, and turning off the compressor and thefan after the first signal is de-asserted.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic representation of a heat-pump system having avariable-capacity compressor according to the principles of the presentdisclosure;

FIG. 2 is a state diagram illustrating another method and algorithm forcontrolling the variable-capacity compressor of FIG. 1;

FIG. 3 is a lookup table that can be used in the method and algorithm ofFIG. 2;

FIG. 4 is another lookup table that can be used in the method andalgorithm of FIG. 2;

FIG. 5 is a graph depicting outdoor ambient temperature and outdoorambient relative humidity versus time of day for an exemplarygeographical location;

FIG. 6 is a table illustrating relative sensible and latent loads forexemplary climate types;

FIG. 7 is a table providing data for a first climate type at varioustimes of a day;

FIG. 8 is a table providing data for a second climate type at varioustimes of a day;

FIG. 9 is a table providing data for a third climate type at varioustimes of a day; and

FIG. 10 is a table providing data for a fourth climate type at varioustimes of a day.

FIG. 11A is a schematic representation of a two-stage climate controlsystem including a variable-capacity compressor, a variable speed indoorfan, and a two-stage thermostat according to the present disclosure.

FIG. 11B depicts possible modes of operation of the two-stage climatecontrol system of FIG. 11A.

FIG. 11C is a schematic representation of a two-stage climate controlsystem including a variable-capacity compressor, a variable speed indoorfan, and a two-stage thermostat with separate compressor capacitycontroller and indoor fan speed controller according to the presentdisclosure.

FIG. 12 shows a timing diagram of the two-stage climate control systemof FIG. 11A.

FIG. 13A is a flowchart of a method for operating the two-stage climatecontrol system of FIGS. 11A and 11C.

FIG. 13B is a flowchart of an additional method for operating thetwo-stage climate control system of FIG. 11C.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

With reference to FIG. 1, a climate-control system 10 is provided thatmay include a variable-capacity compressor (or a variable-capacity groupof compressors) 12, an outdoor heat exchanger 14, an outdoor blower 15,a first expansion device 16, a second expansion device 17, an indoorheat exchanger 18, and an indoor blower 19. In the particularconfiguration shown in FIG. 1, the system 10 is a heat-pump systemhaving a reversing valve 20 operable to control a direction of workingfluid flow through the system 10 to switch the system 10 between aheating mode and a cooling mode. In some configurations, the system 10may be an air-conditioning system or a refrigeration system, forexample, and may be operable in only the cooling mode.

As will be described in more detail below, a controller or controlmodule 22 may control operation of the compressor 12 and may switch thecompressor 12 between a low-capacity mode and a high-capacity mode basedon data received from an outdoor-air-temperature sensor 24, a signalreceived from a thermostat 26, a comparison between a runtime T of thecompressor 12 and a predetermined low-capacity runtime T1, and/or acomparison between a previous high-capacity runtime T2 with apredetermined value. The control module 22 may minimize or reduceemployment of high-capacity-mode operation to minimize or reduce energyusage while maintaining an acceptable level of comfort within a space tobe heated or cooled.

The compressor 12 can be or include a scroll compressor, a reciprocatingcompressor, or a rotary vane compressor, for example, and/or any othertype of compressor. The compressor 12 may be any type ofvariable-capacity compressor that is operable in at least a low-capacitymode and a high-capacity mode. For example, the compressor 12 may be orinclude a multi-stage compressor, a group of independently operablecompressors, a multi-speed or variable-speed compressor (having avariable-speed or multi-speed motor), a compressor having modulatedsuction (e.g., blocked suction), a compressor having fluid-injection(e.g., an economizer circuit), a pulse-width-modulated scroll compressorconfigured for scroll separation (e.g., a digital scroll compressor), acompressor having variable-volume-ratio valves configured to leakintermediate-pressure working fluid, or a compressor having two or moreof the above capacity modulation means. It will be appreciated that thecompressor 12 could include any other additional or alternativestructure for varying its capacity and/or the operating capacity of thesystem 10.

It will be appreciated that the low-capacity and/or high-capacity modesmay be continuous, steady-state operating modes, or compressor 12 may bemodulated (e.g., pulse-width-modulated) during operation in thelow-capacity mode and/or during operation in the high-capacity mode.Exemplary variable-capacity compressors are disclosed in assignee'scommonly owned U.S. Pat. No. 8,616,014, U.S. Pat. No. 6,679,072, U.S.Pat. No. 8,585,382, U.S. Pat. No. 6,213,731, U.S. Pat. No. 8,485,789,U.S. Pat. No. 8,459,053, and U.S. Pat. No. 5,385,453, the disclosures ofwhich are hereby incorporated by reference.

The compressor 12, the outdoor heat exchanger 14, the outdoor blower 15,the first expansion device 16 and the reversing valve 20 may be disposedin an outdoor unit 28. The second expansion device 17, the indoor heatexchanger 18 and the indoor blower 19 may be disposed within an indoorunit 30 (e.g., an air handler or furnace) disposed within a home orother building 32. A first check valve 34 may be disposed betweenoutdoor heat exchanger 14 and the first expansion device 16 and mayrestrict or prevent fluid flow through the first expansion device 16 inthe cooling mode and may allow fluid flow through the first expansiondevice 16 in the heating mode. A second check valve 36 may be disposedbetween the second expansion device 17 and the indoor heat exchanger 18and may restrict or prevent fluid flow through the second expansiondevice 17 in the heating mode and may allow fluid flow through thesecond expansion device 17 in the cooling mode.

The outdoor-air-temperature sensor 24 is disposed outside of thebuilding 32 and within or outside of the outdoor unit 28 and isconfigured to measure an outdoor ambient air temperature and communicatethe outdoor ambient air temperature value to the control module 22intermittently, continuously or on-demand. In some configurations, theoutside-air-temperature sensor 24 could be a thermometer or other sensorassociated with a weather monitoring and/or weather reporting system orentity. In such configurations, the control module 22 may obtain theoutdoor-air temperature (measured by the sensor 24) from the weathermonitoring and/or weather reporting system or entity via, for example,an internet, Wi-Fi, Bluetooth®, Zigbee®, power-line carriercommunication (PLCC), or cellular connection or any other wired orwireless communication protocol.

For example, the control module 22 may communicate with the weathermonitoring and/or weather reporting system or entity over the internetvia a Wi-Fi connection to a Wi-Fi router located in or associated withthe building 32. The thermostat 26 is disposed inside of the building 32and outside of the indoor unit 30 and is configured to measure an airtemperature within a room or space to be cooled or heated by the system10. The thermostat 26 can be a single-stage thermostat, for example,that generates only one type of demand signal in response to atemperature within the room or spaced rising above (in the cooling mode)or falling below (in the heating mode) a setpoint temperature. Thecontrol module 22 could be disposed in any suitable location, such asinside of or adjacent to the outdoor unit 28 or inside of or adjacent tothe indoor unit 30, for example.

In some implementations, for example as shown in FIGS. 11A and 11C, thecontrol module 22 may include two separate controllers: an indoor fanspeed controller and a compressor capacity controller (see elements 504and 502 in FIGS. 11A and 11C). For example, while not shown in FIG. 1,the outdoor unit 28 may include the compressor capacity controller 504,and the indoor unit 30 may include the indoor fan speed controller 502.Further, while not shown, it is understood that a contactor 12-1 (shownin FIGS. 11A and 11C) is associated with the compressor 12 and iscontrolled by the control module 22 or by the compressor capacitycontroller 504 to turn on the compressor 12.

In the cooling mode, the outdoor heat exchanger 14 may operate as acondenser or as a gas cooler and may cool discharge-pressure workingfluid received from the compressor 12 by transferring heat from theworking fluid to air forced over the outdoor heat exchanger 14 by theoutdoor blower 15, for example. The outdoor blower 15 could include afixed-speed, multi-speed or variable-speed fan. In the cooling mode, theindoor heat exchanger 18 may operate as an evaporator in which theworking fluid absorbs heat from air forced over the indoor heatexchanger 18 by the indoor blower 19 to cool a space within the home orbuilding 32. The indoor blower 19 could include a fixed-speed,multi-speed or variable-speed fan. In the heating mode, the outdoor heatexchanger 14 may operate as an evaporator, and the indoor heat exchanger18 may operate as a condenser or as a gas cooler and may transfer heatfrom working fluid discharged from the compressor 12 to a space to beheated.

Referring now to FIG. 2, a method and control algorithm 300 will bedescribed that can be executed by the control module 22. The algorithm300 may control operation of the compressor 12 and switch the compressor12 between the low-capacity and high-capacity modes. In an initial state310, the compressor 12 may be off. The thermostat 26 may send a demandsignal Y to the control module 22 in response to an air temperature inthe space to be heated or cooled by the system 10 dropping below (in theheating mode) or rising above (in the cooling mode) a selected setpointtemperature. In response to receipt of the demand signal Y, the controlmodule 22 may initiate operation of the compressor 12 in thelow-capacity mode (state 340) and simultaneously, at state 320, read anoutdoor air temperature (received from sensor 24 at input 330) and set alow-capacity runtime T1 based on data from table 345 (FIG. 3).Thereafter, the compressor 12 may continue to run in the low-capacitymode until the cooling demand is satisfied (i.e., the temperature in thespace to be cooled drops below the selected setpoint temperature asindicated by the thermostat 26 and the thermostat switches the demandsignal Y to “off”), until the total runtime T of the compressor 12 sincethe receipt of the demand signal Y surpasses the low-capacity runtime T1set at state 320, or until the compressor 12 or system 10 is manuallyshutdown or a diagnostic or protection algorithm overrides the algorithm300.

If demand is satisfied before the total runtime T reaches thepredetermined low-capacity runtime T1, the control module 22 mayshutdown the compressor 12 (state 350). If the compressor 12 has beenrunning for longer than the predetermined low-capacity runtime T1without satisfying the demand, the control module 22 may switch thecompressor 12 from the low-capacity mode to the high-capacity mode(state 360). The compressor 12 may continue to run in the high-capacitymode until the cooling demand is satisfied (or until the compressor 12or system 10 is manually shutdown or a diagnostic or protectionalgorithm overrides the algorithm 100). When demand is satisfied, thecontrol module 22 may shutdown the compressor 12 (state 350). When thecompressor 12 is shut down after satisfying demand by operating in thehigh-capacity mode, the control module 22 may record the runtime T2 ofthe compressor 12 in the high-capacity mode and store the high-capacityruntime T2 in a memory module associated with the control module 22.

FIG. 3 depicts the table 345 from which the control module 22 determinesthe low-capacity runtime T1. First, the control module 22 determinesfrom which row of the table 345 to read based on the outdoor ambienttemperature (OAT) value received at input 330. That is, the row of thetable 345 from which the control module 22 reads is the row having anOAT range that includes the OAT value received at input 330. If thecontrol module 22 has not received a demand signal Y from the thermostat26 in a relatively long predetermined period of time (e.g., days, weeksor longer), the control module 22 may initially set the low-capacityruntime T1 at a default or baseline value listed in the Baseline T1column at the corresponding OAT row of table 345.

With the low-capacity runtime T1 set at the baseline value correspondingto the OAT at the time of the initiation of the demand signal Y, thecontrol module 22 may cause the compressor 12 to run in the low-capacitymode (state 340) until demand is met or until the compressor runtime Tsurpasses the set low-capacity runtime T1. If demand has not been metwhen the runtime T reaches the set low-capacity runtime T1, the controlmodule 22 may switch the compressor 12 to the high-capacity mode (state360). The compressor 12 may continue operating in the high-capacity modeuntil demand is met. Once demand is met, the controller 22 may record inthe high-capacity runtime T2, as described above.

Upon receipt of a subsequent demand signal Y, the control module 22 mayagain determine a low-capacity runtime value T1 from the table 345. Thistime, the control module 22 may determine if the OAT falls within one ofa plurality of override ranges 347. For example, override ranges 347 inthe cooling mode may include 85-90° F. and >90° F., and override ranges347 in the heating mode may include 40-45° F. and <40° F. If the OATvalue received at input 330 falls within one of the override ranges 347,the control module 22 may set the low-capacity runtime T1 at an overridevalue determined by referencing the override T1 column at thecorresponding OAT row.

The override value for the low-capacity runtime T1 may be determinedbased on a previous high-capacity runtime T2 _(n-1). For example, if theprevious high-capacity runtime T2 _(n-1) is greater than a predeterminevalue (e.g., five minutes), the control module 22 may set thelow-capacity runtime T1 to a first value (e.g., a short time period suchas five seconds). If the previous high-capacity runtime T2 _(n-1) isless than the predetermine value (e.g., five minutes), the controlmodule 22 may set the low-capacity runtime T1 to a second value (e.g., alonger time period such as twenty minutes or forty minutes). The controlmodule 22 may then cause the compressor 12 to run in the low-capacitymode (state 340) until demand is met or until the compressor runtime Treaches the low-capacity runtime T1, at which time the control module 22may switch the compressor to the high-capacity mode (state 360).

If the OAT falls within an OAT range that is not one of the overrideranges 347, then the control module 22 will continue to set thelow-capacity runtime T1 at the baseline value listed in the baseline T1column. As described above, the control module 22 may cause thecompressor 12 to run in the low-capacity mode until demand is met oruntil the compressor runtime T reaches the low-capacity runtime T1, atwhich time the control module 22 may switch the compressor 12 to thehigh-capacity mode until demand is met.

In another configuration, the algorithm 300 may include determining thelow-capacity runtime T1 based on table 445 (FIG. 4) instead of table345. As described above, the control module 22 may continuously orintermittently receive OAT data from the sensor 24 and may store the OATdata in a memory module. As described above, once the demand signal Y isreceived, the control module 22 may, at state 320, read the current OAT(from input 330) and set the low-capacity runtime T1 from the table 445.

If the control module 22 has not received a demand signal Y from thethermostat 26 in a relatively long predetermined period of time (e.g.,days, weeks or longer), the control module 22 may initially set thelow-capacity runtime T1 at a default or baseline value listed inBaseline T1 column 446 at the OAT row of table 445 that corresponds tothe current OAT received at input 330. With the low-capacity runtime T1set at the baseline value, the control module 22 may then cause thecompressor 12 to operate in the low-capacity mode (state 340) untildemand is met, or until the compressor runtime T reaches the setlow-capacity runtime T1, at which time the control module 22 will runthe compressor 12 in the high-capacity mode (state 360) until demand ismet, in accordance with the algorithm 300 described above. The controlmodule 22 may record the high-capacity runtime T2 for each run cycle ofthe compressor 12.

Upon receipt of a subsequent demand signal Y, the control module 22 mayagain determine a low-capacity runtime value T1 from the table 445. Thistime, the control module 22 may read the current OAT and determine aslope of the OAT over a predetermined time period (e.g., over the lasttwenty minutes, but may be any predetermined period of time that issuitably indicative of system conditions). If the OAT slope is within aneutral slope range (where the slope is greater than −0.3 degrees per 20minutes and less than 0.3 degrees per 20 minutes, for example), then thecontrol module 22 may set the low-capacity runtime T1 at the baselinevalue listed in the Baseline T1 column 446 at the OAT row of table 445that corresponds to the current OAT. If the OAT slope is within apositive slope range (where the slope is greater than 0.3 degrees per 20minutes, for example), then the control module 22 may set thelow-capacity runtime T1 at the value listed in the Positive OAT Slopecolumn 447 at the OAT row of table 445 that corresponds to the currentOAT. If the OAT slope is within a first negative slope range (where theslope is less than −0.3 degrees per 20 minutes and greater than −0.6degrees per 20 minutes, for example), then the control module 22 may setthe low-capacity runtime T1 at the value listed in the Negative OATSlope column 448 at the OAT row of table 445 that corresponds to thecurrent OAT. If the OAT slope is within a second negative slope range(where the slope is less than −0.6 degrees per 20 minutes, for example),then the control module 22 may set the low-capacity runtime T1 at thevalue listed in the Extreme Negative OAT Slope column 449 at the OAT rowof table 445 that corresponds to the current OAT.

While the OAT slope is described above as being determined over apredetermined time period, the OAT slope could also be determined bycomparing OAT values at the beginning of a current compressor operatingcycle (i.e., when the current demand signal Y is received) and at theend of the previous compressor operating cycle (i.e., when the lastdemand signal Y switched off). Still other methods for determining theOAT slope could be employed.

As shown in FIG. 4, some or all of the rows of column 447 and column 448include steps for determining the low-capacity runtime T1 based on theprevious high-capacity runtime T2 _(n-1) (i.e., the high-capacityruntime T2 of the previous run cycle in which the demand signal Y wasconstantly on or demand for heating or cooling was constantly present).For example, in the row of the Positive OAT Slope column 447corresponding to an OAT of greater than 90° F.: if the previoushigh-capacity runtime T2 _(n-1) was greater than five minutes, then thecurrent low-capacity runtime T1 _(n) should be set to five seconds; andif the previous high-capacity runtime T2 _(n-1) was less than or equalto five minutes, then the current low-capacity runtime T1 _(n) should beset to thirty minutes. As shown in FIG. 4, the above time andtemperature values may vary for the various rows of columns 447 and 448.

Further, as shown in FIG. 4, the Extreme Negative OAT Slope column 449may simply include predetermined values for each OAT range that may notbe dependent upon a previous high-capacity runtime. In someconfigurations, the Extreme Negative OAT Slope column 449 may refer thealgorithm to the Negative OAT Slope column 448 for colder OAT ranges(e.g., below 45° F.). For example, if the OAT slope is less than −0.6degrees per 20 minutes and the current OAT is less than 45° F., thecontrol module 22 may set the low-capacity runtime T1 in accordance withthe Negative OAT Slope column 448.

After setting the low-capacity runtime T1 in accordance with table 445,the control module 22 may operate the compressor 12 in the low-capacitymode (state 340) until demand is met, or until the compressor runtime Treaches the set low-capacity runtime T1 (at which time the controlmodule 22 will switch the compressor to the high-capacity mode untildemand is met), in accordance with the algorithm 300 described above.

OAT slope is generally a good indicator or estimate of the time of day.Therefore, adjusting low-capacity and high-capacity runtimes based onOAT slope effectively adjusts low-capacity and high-capacity runtimes toaccount for the diurnal temperature profile. That is, during the courseof a day, the OAT often changes according to a fairly standard profile.When the OAT is rising in the morning, the total compressor runtime T istypically shorter (during the cooling season) than when the OAT isfalling in the evening because the house or building in which the system10 is installed has accumulated a thermal load throughout the day thatis still present in the evening. For the heating mode, the load shiftsto early morning, i.e., more high-capacity runtime during positive slopeperiods or early morning part of day, and less low-capacity runtimeduring negative slope periods or evenings, since the house or buildingabsorbs heat during the day. Therefore, adjusting the low-capacity andhigh-capacity runtimes based on OAT slope or time of day accounts forthe thermal load on the house or building and increases comfort for theoccupants.

Furthermore, outdoor ambient relative humidity (OARH) often rises as OATdecreases and falls as OAT increases (as shown in FIG. 5). Therefore,OAT slope also indicates or approximates the slope of OARH. Thus,extreme negative OAT slopes (e.g., OAT slope less than −0.6 degrees per20 minutes) can indicate an increased demand for dehumidification due toa mid-afternoon rain event, for example. Therefore, determining the OATslope and adjusting low-capacity and high-capacity runtimes based on theOAT slope allows the algorithm 300 to account for the thermal load ofthe house or building and thermal load delay due to diurnal profile andallows the algorithm 300 to account for slope of ambient relativehumidity without the use of a relative humidity sensor.

FIG. 5 depicts the OAT and OARH profile for a given day at a givenlocation. As shown in FIG. 5, a mid-afternoon rain event can beaccompanied by a sharp decrease in OAT and a corresponding sharpincrease in OARH. Therefore, even though the OAT has decreased as aresult of the rain event, demand for cooling may remain high due to theincreased humidity and the possibility of OAT returning to its previoushigh before sunset. Therefore, such events having an extreme negativeOAT slope are accounted for in table 445 (FIG. 4) at the ExtremeNegative OAT Slope column 449, which assigns a very short low-capacityruntime T1 regardless of the length of any previous high-capacityruntime.

As described above, the indoor blower 19 (FIG. 1) could be a multi-speedblower that can be set at two or more speeds. Therefore, the system 10may be operable in at least four different modes. In a first mode, thecompressor 12 may operate in the low-capacity mode, and the indoorblower 19 may operate at a low speed. In a second mode, the compressor12 may operate in the low-capacity mode, and the indoor blower 19 mayoperate at a high speed. In a third mode, the compressor 12 may operatein the high-capacity mode, and the indoor blower 19 may operate at thelow speed. In a fourth mode, the compressor 12 may operate in thehigh-capacity mode, and the indoor blower 19 may operate at the highspeed.

In some configurations, the speed of the indoor blower 19 may be setmanually (e.g., by an installation contractor) and thereafter, the speedof the indoor blower 19 may be fixed at that speed. The speed of theindoor blower 19 could be selected based on the climate of the region(specifically, temperatures and humidity levels) in which the system 10is installed. For example, as shown in FIG. 6, in regions with hot andhumid climates (e.g., sub-tropical and tropical climates), the indoorblower 19 may be set to the low setting because lower indoor blowerspeeds are advantageous for faster dehumidification. In regions withvery hot and dry climates (e.g., desert climates like the SouthwestUnited States), the indoor blower 19 may be set to the high settingbecause higher indoor blower speeds are more advantageous for quicklyreducing sensible heat. In regions with mixed temperatures and mildhumidity, the indoor blower 19 may be set to the low or medium setting.In regions with mixed temperatures and higher humidity, the indoorblower 19 may be set to the low setting.

In the configurations in which the speed of the indoor blower 19 is setat installation and is fixed thereafter, the system 10 (havingvariable-capacity compressor 12) can be modulated between two modes:either between the first and third modes described above or between thesecond and fourth modes described above.

In other configurations, the control module 22 may be in communicationwith the indoor blower 19 and may be configured to modulate the speed ofthe indoor blower 19. In such configurations, the control module 22 maybe configured to switch the system 10 among the first, second, third andfourth modes (i.e., by modulating the compressor 12 between thelow-capacity and high-capacity modes and by modulating the indoor blower19 between high and low speeds). The control module 22 may switch amongthe first, second, third and fourth modes depending on OAT, OAT slope,time of day, low-capacity and high-capacity runtimes T1, T2, indoorrelative humidity, outdoor relative humidity, historical weather dataand/or forecasted weather data, for example.

It will be appreciated that the tables 345 and 445 and runtimes T1, T2could also be adjusted based on the climate of the region in which thesystem 10 is installed. FIGS. 7-10 provide overviews of the exemplaryregions of FIG. 6 including low-capacity/high-capacity (Y1/Y2)compressor settings, OAT slopes, sensible loads and latent loads atvarious times of the day.

In other configurations, a two-stage system may include a variablecapacity compressor such as the compressor 12 and a variable speedindoor fan such as the indoor blower 19 shown in FIG. 1 and a two-stagethermostat 26-1 shown in FIG. 11A and described below. The two-stagethermostat 26-1 can provide two control signals, which are referencedherein as a first control signal Y1 and a second control signal Y2. Thefirst control signal Y1 is similar to the demand signal Y describedabove with reference to FIGS. 1-10. The two-stage thermostat 26-1generates the second control signal Y2 when the indoor load cannot bematched by operating the compressor 12 in the high-capacity mode (e.g.,when more than normal sensible cooling is needed).

The two-stage system operates as described above with reference to FIGS.1-10 as long as the two-stage thermostat 26-1 asserts only the firstcontrol signal Y1. Specifically, when only the first control signal Y1is asserted, the two-stage system selects an operating mode of thecompressor 12 (i.e., low or high-capacity mode) based on the outdoorambient temperature (OAT) and switches the operating mode of thecompressor 12 to the high-capacity mode when the runtime of thecompressor 12 in the low-capacity mode is exceeded. Additionally, whenonly the first control signal Y1 is asserted, the indoor blower 19(hereinafter the indoor fan 19) is operated only at a low speed althoughthe compressor 12 is operated in both low and high-capacity modes. Theindoor fan 19 is operated at a high speed only during the time periodwhen the second control signal Y2 is asserted.

When the two-stage thermostat 26-1 asserts the second control signal Y2(either after Y1 is asserted or independently of Y1 (i.e., when Y1 isnot first asserted as explained below), the two-stage system suspends oroverrides normal operation described above with reference to FIGS. 1-10and immediately switches the operation of the compressor 12 to thehigh-capacity mode. Additionally, the two-stage system switches thespeed of the indoor fan 19 to the high speed.

Thereafter, if the two-stage thermostat 26-1 determines that the secondcontrol signal Y2 is no longer needed (e.g., after a period of time whenthe indoor load is sufficiently reduced), the two-stage thermostat 26-1de-asserts or withdraws the second control signal Y2 and the firstcontrol signal Y1 remains asserted. When the second control signal Y2 isde-asserted, the speed of the indoor fan 19 is switched to the lowspeed. However the compressor 12 continues to operate in thehigh-capacity mode until the first control signal Y1 is de-asserted, atwhich point both the compressor 12 and the indoor fan 19 are turned off.

FIGS. 11A and 11B depict an example of a two-stage system 500 includingthe variable capacity compressor such as the compressor 12, a variablespeed indoor fan such as the indoor fan 19, and the two-stage thermostat26-1. In FIG. 11A, the two-stage system 500 includes a controller 22-1that controls the compressor 12 (and an associated contactor 12-1) andthe indoor fan 19 based on the first control signal Y1 and the secondcontrol signal Y2 received from the two-stage thermostat 26-1 and asignal indicating the OAT received from the outdoor temperature sensor24 as follows.

The controller 22-1 includes an indoor fan speed controller 502 and acompressor capacity controller 504. The indoor fan speed controller 502and the compressor capacity controller 504 receive the first controlsignal Y1 and the second control signal Y2 received from the two-stagethermostat 26-1. The compressor capacity controller 504 also receives asignal from the outdoor temperature sensor 24 indicating OAT.

When only the first control signal Y1 is asserted and the second controlsignal Y2 is not asserted, the controller 22-1 operates the compressor12 and the indoor fan 19 as described above with reference to FIGS.1-10. As explained below, the indoor fan speed controller 502 controlsthe speed of the indoor fan 19 based on the first and second controlsignals Y1 and Y2; and the compressor capacity controller 504 controlsthe operating mode of the compressor 12 based on the following: thefirst and second control signals Y1 and Y2, the outdoor ambienttemperature (OAT), and the indoor load determined by the two-stagethermostat 26-1 based on the indoor temperature sensed by a temperaturesensor 27.

FIG. 11B shows 4 possible modes in which the two-stage system 500 canoperate. When the two-stage system 500 operates in mode 1, thecompressor 12 operates in the low-capacity mode, and the indoor fan 19operates at the low speed. When the two-stage system 500 operates inmode 2, the compressor 12 operates in the high-capacity mode, and theindoor fan 19 operates at the low speed. When the two-stage system 500operates in mode 4, the compressor 12 operates in the high-capacitymode, and the indoor fan 19 operates at the high speed. In someconfigurations, the two-stage system 500 may not operate in mode 3,where the compressor 12 may operate in the low-capacity mode, and theindoor fan 19 may operate in the high speed.

FIG. 11C shows another example of the two-stage system 500 (shown as500-1), wherein the indoor fan speed controller 502 and the compressorcapacity controller 504 are physically separate units.

FIG. 12 shows a timing diagram 550 of the two-stage system 500. Theoperation of the two-stage system 500 is now described with reference tothe timing diagram 550. The same description applies to the two-stagesystem 500-1 as well. Initially, that is before 552, the compressor 12and the indoor fan 19 are turned off. At 552, the two-stage thermostat26-1 asserts the first control signal Y1 based on detecting a firstcondition relating to the indoor temperature. For example, the two-stagethermostat 26-1 asserts the first control signal Y1 based on detecting afirst demand for changing the indoor temperature by a first amount whenthe indoor temperature differs from a desired temperature setting on thetwo-stage thermostat 26-1 by the first amount. At this point (i.e. at552), the second control signal Y2 remains de-asserted.

When only the first control signal Y1 is asserted at 552, the compressorcapacity controller 504 activates the compressor contactor at 554, whichturns on the compressor 12 in the low-capacity mode. Additionally, theindoor fan speed controller 502 turns on the indoor fan 19 at the lowspeed at 556. Accordingly, the two-stage system 500 operates in mode 1at 552 (i.e., the compressor 12 operates in the low-capacity mode, andthe indoor fan 19 operates at the low speed).

Thereafter, as long as the two-stage thermostat 26-1 does not assert(i.e., until the two-stage thermostat 26-1 asserts) the second controlsignal Y2, the two-stage system 500 operates normally as described abovewith reference to FIGS. 1-10 based on the outdoor ambient temperature(OAT) indicated by the signal from the outdoor temperature sensor 24.Accordingly, the compressor capacity controller 504 switches theoperating mode of the compressor 12 to the high-capacity mode at 558 (byactivating a compressor solenoid or a suitable mechanism at 560) whenthe runtime of the compressor 12 in the low-capacity mode is exceeded.The run time of the compressor 12 in the low-capacity mode may be afirst predetermined time period (from 552 to 558) that can be selectedas described above with reference to FIGS. 1-10. The indoor fan 19continues to operate at the low speed. Accordingly, the two-stage system500 operates in mode 2 at 558 (i.e., the compressor 12 operates in thehigh-capacity mode, and the indoor fan 19 operates at the low speed).

At 562, the two-stage thermostat 26-1 asserts the second control signalY2 based on detecting a second demand for changing the indoortemperature by a second amount when the indoor temperature differs froma desired temperature setting on the two-stage thermostat 26-1 by thesecond amount. For example, after the compressor 12 and the indoor fan19 have been running respectively in the high-capacity mode and the lowspeed for a second predetermined period of time (from 558 to 562), thetwo-stage thermostat 26-1 may determine that the indoor load is stillsignificantly high or that the indoor load is not reducing at a desiredrate. That is, the two-stage thermostat 26-1 may determine that thetemperature difference between the indoor temperature and the desiredtemperature setting on the on the two-stage thermostat 26-1 is stillgreater than or equal to a predetermined amount. Accordingly, thetwo-stage thermostat 26-1 may assert the second control signal Y2 at562.

As soon as the second control signal Y2 is asserted at 562, the indoorfan speed controller 502 switches the speed of the indoor fan 19 to thehigh speed as shown at 564 and 566 to help reduce the indoor load at afaster rate. That is, the indoor fan speed controller 502 switches thespeed of the indoor fan 19 to reduce the difference between the indoortemperature and the desired temperature setting on the on the two-stagethermostat 26-1 to less than or equal to a predetermined amount. Thecompressor capacity controller 504 keeps the compressor 12 running inthe high-capacity mode at 562. Accordingly, the two-stage system 500operates in mode 4 (i.e., the compressor 12 operates in thehigh-capacity mode, and the indoor fan 19 operates at the high speed).

The two-stage thermostat 26-1 keeps the second control signal Y2asserted for a third predetermined period of time (from 562 to 568) andde-asserts the second control signal Y2 at 568 after the thirdpredetermined time period. The two-stage thermostat 26-1 keeps thesecond signal Y2 asserted until the indoor temperature differs from thedesired temperature by less than or equal to a predetermined amount andde-asserts the second signal Y2 after the indoor temperature differsfrom the desired temperature by less than or equal to the predeterminedamount at 568.

As soon as the second control signal Y2 is de-asserted at 568, theindoor fan speed controller 502 switches the speed of the indoor fan 19to the low speed as shown at 570 and 572. The compressor capacitycontroller 504 keeps the compressor 12 running in the high-capacity modeat 568. Accordingly, the two-stage system 500 operates in mode 2 (i.e.,the compressor 12 operates in the high-capacity mode, and the indoor fan19 operates at the low speed).

At 574, the two-stage thermostat 26-1 detects that the indoortemperature is equal to the desired temperature setting on the two-stagethermostat 26-1. Accordingly, the two-stage thermostat 26-1 de-assertsthe first control signal Y1. As soon as the first control signal Y1 isde-asserted, the indoor fan speed controller 502 and the compressorcapacity controller 504 respectively turn off the indoor fan 19 and thecompressor 12 as shown at 576 through 582. The operation from 552through 582 is repeated based on the first and second control signals Y1and Y2 and the OAT sensed by the outdoor temperature sensor 24.

In some instances, the indoor load may change drastically, suddenly, orunexpectedly due to unusual events. For example, an occupant of a house,of which the climate is being controlled by the two-stage system 500,may open a window or door for an extended period of time; one or moreoccupants of the house may take extended showers or clean carpeting;many people may attend a party at the house; and so on. As anotherexample, a person may enter the house after experiencing harshertemperatures (e.g., extreme heat or cold) outside than inside the houseand therefore may drastically change the desired temperature setting onthe two-stage thermostat 26-1 (e.g., to much lower than normal settingfor faster cooling or much greater than normal setting for fasterheating). As yet another example, the two-stage thermostat 26-1 mayinclude a setback feature that allows for different temperature settingsat different time periods. For example, if the house is unoccupiedduring the day, the two-stage thermostat 26-1 may be set such that theindoor temperature is warmer during days than nights in summer andcooler during days than nights in winter. Additionally, the two-stagethermostat 26-1 may allow different settings on weekends than weekdayswhen occupants stay indoors during the day.

In such instances, the two-stage thermostat 26-1 may detect a sudden,greater than normal increase in the indoor load due to one or moreunusual events of the kind described above and in response may assertthe second control signal Y2 instead of, and/or in addition to,asserting the first control signal Y1. As soon as the second controlsignal Y2 is asserted, the compressor capacity controller 504 turns onand operates the compressor 12 directly in the high-capacity mode, andthe indoor fan speed controller 502 turns on and operates the indoor fan19 directly at the high speed.

Accordingly, the two-stage system 500 operates in mode 4 (i.e., thecompressor 12 operates in the high-capacity mode, and the indoor fan 19operates at the high speed). After a predetermined time period, when adifference between the indoor temperature and the desired temperaturesetting on the two-stage thermostat 26-1 is less than or equal to apredetermined amount (i.e., when the indoor load is reduced to less thanor equal to a predetermined amount), the two-stage thermostat 26-1de-asserts the second control signal Y2 and asserts the first controlsignal Y1.

As soon as the second control signal Y2 is de-asserted and the firstcontrol signal Y1 is asserted, the compressor capacity controller 504keeps operating the compressor 12 in the high-capacity mode, and theindoor fan speed controller 502 switches the speed of the indoor fan 19to the low speed. Accordingly, the two-stage system 500 operates in mode2 (i.e., the compressor 12 operates in the high-capacity mode, and theindoor fan 19 operates at the low speed).

Thereafter, when the two-stage thermostat 26-1 detects that the indoortemperature is equal to the desired temperature setting on the two-stagethermostat 26-1, the two-stage thermostat 26-1 de-asserts the firstcontrol signal Y1. As soon as the first control signal Y1 isde-asserted, the indoor fan speed controller 502 and the compressorcapacity controller 504 respectively turn off the indoor fan 19 and thecompressor 12. Subsequently, the operation from 552 through 582 shown inand described with reference to FIG. 12 is repeated based on the firstand second control signals Y1 and Y2 and the OAT sensed by the outdoortemperature sensor 24.

Thus, the two-stage system 500 can perform climate control based onmonitoring of a combination of the outdoor and indoorloads/temperatures. Additionally, the two-stage system 500 may provide asystem override feature based on the second control signal Y2 providedby the two-stage thermostat. The two-stage system 500 provides bothlatent cooling and sensible cooling benefits, where latent coolingcorresponds to humidity reduction, and sensible cooling corresponds toheat removal. The two-stage system 500 provides latent cooling throughmode 2 operation, where the compressor is operated in the high-capacitymode and the indoor fan is operated at the low speed, which helps inreducing humidity. The two-stage system 500 provides sensible coolingthrough mode 4 operation, where the compressor is operated in thehigh-capacity mode and the indoor fan is operated at the high speed,which helps in fast heat removal.

FIG. 13A shows a method 600 for operating a two-stage system (e.g., thetwo-stage systems 500 and 500-1) including a variable capacitycompressor such as the compressor 12, a variable speed indoor fan suchas the indoor fan 19, and a two-stage thermostat such as the two-stagethermostat 26-1. At 602, with the compressor and the indoor faninitially being turned off, control determines whether the two-stagethermostat asserts the first control signal Y1 or the second controlsignal Y2.

At 604, in response to the first control signal Y1 being asserted andthe second control signal Y2 not being asserted, control turns on thecompressor 12 and the indoor fan 19 and operates the compressor in thelow-capacity mode and the indoor fan at the low speed (i.e., mode 1). At606, control determines whether the second control signal Y2 isasserted. At 608, in response to the second control signal Y2 not beingasserted, control determines whether the compressor runtime in thelow-capacity mode is exceeded, as described above. Control returns to604 if the compressor runtime in the low-capacity mode is not exceeded.At 610, if the compressor runtime in the low-capacity mode is exceeded,control determines whether the second control signal Y2 is asserted. At612, in response to the second control signal Y2 not being asserted,control operates the compressor 12 in the high-capacity mode and theindoor fan 19 at the low speed (i.e., mode 2).

At 614, control determines whether the first control signal Y1 isde-asserted. Control returns to 610 if the first control signal Y1 isnot de-asserted. At 616, if the first control signal Y1 is de-asserted,control turns off the compressor 12 and the indoor fan 19, and controlreturns to 602.

At 618, if the two-stage thermostat asserts the second control signal Y2at 606 or 610, control operates the compressor 12 in the high-capacitymode and the indoor fan 19 at the high speed (i.e., mode 4). At 620,control determines whether the second control signal Y2 is de-asserted.Control returns to 612 if the second control signal Y2 is de-asserted.Control returns to 618 if the second control signal Y2 is notde-asserted.

At 622, when the compressor and the indoor fan are initially turned off,if at 602 the two-stage thermostat 26-1 asserts the second controlsignal Y2 instead of and/or in addition to the first control signal Y1,control turns on the compressor 12 and the indoor fan 19 and operatesthe compressor 12 in the high-capacity mode and the indoor fan 19 at thehigh speed (i.e., mode 4). At 624 control determines whether the secondcontrol signal Y2 is de-asserted and the first control signal Y1 isasserted. Control returns to 622 if the second control signal Y2 is notde-asserted and the first control signal Y1 is not asserted. At 626, ifthe second control signal Y2 is de-asserted and the first control signalY1 is asserted, control operates the compressor 12 in the high-capacitymode and the indoor fan 19 at the low speed (i.e., mode 2). At 628,control determines whether the first control signal Y1 is de-asserted.Control returns to 626 if the first control signal Y1 is notde-asserted. At 630, if the first control signal Y1 is de-asserted,control turns off the compressor 12 and the indoor fan 19, and controlreturns to 602.

FIG. 13B shows another method 600-1 for operating a two-stage system(e.g., the two-stage systems 500 and 500-1) including a variablecapacity compressor such as the compressor 12, a variable speed indoorfan such as the indoor fan 19, and a two-stage thermostat such as thetwo-stage thermostat 26-1. At 650, control determines whether thecompressor and the indoor fan are initially turned off. At 652, controladditionally determines whether the two-stage thermostat asserts thefirst control signal Y1 and also the second control signal Y2. At 654,control additionally determines whether the outdoor temperature isgreater than or equal to a predetermined threshold.

At 656, if all of the above three conditions are satisfied, controldirectly operates the compressor 12 in the high-capacity mode and theindoor fan 19 at the high speed (i.e., mode 4). At 658, controldetermines whether the second control signal Y2 is de-asserted andwhether the first control signal Y1 still remains asserted. Controlcontinues to operate the compressor 12 in the high-capacity mode and theindoor fan 19 at the high speed (i.e., mode 4) if both the first andsecond control signals Y1 and Y2 continue to remain asserted (i.e., ifthe second control signal Y2 is not de-asserted and if the first controlsignal Y1 still remains asserted).

At 660, if the second control signal Y2 is de-asserted and if the firstcontrol signal Y1 still remains asserted, control continues to operatethe compressor 12 in the high-capacity mode and operates the indoor fan19 at the low speed (i.e., mode 2). At 662, control determines whetherthe first control signal Y1 is also de-asserted. Control returns to 660if the first control signal Y1 is not de-asserted (i.e., still remainsasserted). At 664, if the first control signal Y1 is also de-asserted,control turns off the compressor 12 and the indoor fan 19.

Accordingly, as described in various embodiments above, a systemaccording to the present disclosure includes a compressor, an indoorfan, a thermostat, an indoor fan controller, and a compressorcontroller. The thermostat provides first and second signals based onindoor loading. The fan controller operates the fan in low speed modeand the compressor controller operates the compressor in low capacitymode when only the first signal is asserted. The compressor controllerautomatically switches the compressor to high capacity mode if only thefirst signal remains asserted past the low capacity mode runtime. Thefan controller operates the fan in high speed mode when the secondsignal is asserted while the first signal is still asserted. Thecompressor controller continues to operate the compressor in highcapacity mode and the fan controller operates the fan in low speed modeafter the second signal is de-asserted, until the first signal isde-asserted, at which point the fan and compressor are turned off. Thecontrollers operate the compressor and fan directly from a stoppedcondition in high capacity mode and high speed when the first and secondsignals are asserted and the outdoor temperature exceeds a thresholdvalue, and then in high capacity mode and low speed when the secondsignal is de-asserted while the first signal is still asserted, untilthe first signal is de-asserted.

The two-stage systems 500 and 500-1 provide many benefits. For example,in the absence of the second control signal Y2, the capacity of thecompressor 12 is switched based on OAT. This allows for proactivecompressor capacity switching in response to temperature changes sincethe indoor load is relatively static in nature and follows OAT and istherefore predictable. The two-stage system 500 retains thediurnal/slope based capacity selection of the compressor as describedwith reference to FIGS. 1-10 for load matching. The two-stage systems500 and 500-1 also retain the latent cooling benefits through mode 2operation, where the compressor is operated in the high-capacity modeand the indoor fan is operated at the low speed, which helps in reducinghumidity.

Further, the two-stage thermostat 26-1 provides the following benefits.It allows users to manually override the normal operation by manuallysetting high demand, to which the two-stage system responds by directlyoperating the compressor 12 in the high-capacity mode and the indoor fan19 at the high speed (i.e., mode 4), which provides immediate sensiblecooling benefit. Subsequently, the two-stage system keeps the compressor12 operating in the high-capacity mode and operates the indoor fan 19 atthe low speed, which again offers the latent cooling benefits byreducing humidity. The two-stage system can perform similar operation ifthe two-stage thermostat 26-1 includes a setback feature that can beused to assert high demand manually or by programming. The two-stagesystem also changes the speed of the indoor fan to match the indoorsensible cooling load.

The present disclosure describes a two-stage cooling system for exampleonly. The teachings of the present disclosure apply equally to atwo-stage heating system and to a two-stage heat pump system.

In this application, including the definitions below, the term “module”or the term “controller” may be replaced with the term “circuit.” Theterm “module” may refer to, be part of, or include: an ApplicationSpecific Integrated Circuit (ASIC); a digital, analog, or mixedanalog/digital discrete circuit; a digital, analog, or mixedanalog/digital integrated circuit; a combinational logic circuit; afield programmable gate array (FPGA); a processor circuit (shared,dedicated, or group) that executes code; a memory circuit (shared,dedicated, or group) that stores code executed by the processor circuit;other suitable hardware components that provide the describedfunctionality; or a combination of some or all of the above, such as ina system-on-chip.

The module may include one or more interface circuits. In some examples,the interface circuits may include wired or wireless interfaces that areconnected to a local area network (LAN), the Internet, a wide areanetwork (WAN), or combinations thereof. The functionality of any givenmodule of the present disclosure may be distributed among multiplemodules that are connected via interface circuits. For example, multiplemodules may allow load balancing. In a further example, a server (alsoknown as remote, or cloud) module may accomplish some functionality onbehalf of a client module.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes, datastructures, and/or objects. The term shared processor circuitencompasses a single processor circuit that executes some or all codefrom multiple modules. The term group processor circuit encompasses aprocessor circuit that, in combination with additional processorcircuits, executes some or all code from one or more modules. Referencesto multiple processor circuits encompass multiple processor circuits ondiscrete dies, multiple processor circuits on a single die, multiplecores of a single processor circuit, multiple threads of a singleprocessor circuit, or a combination of the above. The term shared memorycircuit encompasses a single memory circuit that stores some or all codefrom multiple modules. The term group memory circuit encompasses amemory circuit that, in combination with additional memories, storessome or all code from one or more modules.

The term memory circuit is a subset of the term computer-readablemedium. The term computer-readable medium, as used herein, does notencompass transitory electrical or electromagnetic signals propagatingthrough a medium (such as on a carrier wave); the term computer-readablemedium may therefore be considered tangible and non-transitory.Non-limiting examples of a non-transitory, tangible computer-readablemedium are nonvolatile memory circuits (such as a flash memory circuit,an erasable programmable read-only memory circuit, or a mask read-onlymemory circuit), volatile memory circuits (such as a static randomaccess memory circuit or a dynamic random access memory circuit),magnetic storage media (such as an analog or digital magnetic tape or ahard disk drive), and optical storage media (such as a CD, a DVD, or aBlu-ray Disc).

The apparatuses and methods described in this application may bepartially or fully implemented by a special purpose computer created byconfiguring a general purpose computer to execute one or more particularfunctions embodied in computer programs. The functional blocks,flowchart components, and other elements described above serve assoftware specifications, which can be translated into the computerprograms by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that arestored on at least one non-transitory, tangible computer-readablemedium. The computer programs may also include or rely on stored data.The computer programs may encompass a basic input/output system (BIOS)that interacts with hardware of the special purpose computer, devicedrivers that interact with particular devices of the special purposecomputer, one or more operating systems, user applications, backgroundservices, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed,such as HTML (hypertext markup language) or XML (extensible markuplanguage), (ii) assembly code, (iii) object code generated from sourcecode by a compiler, (iv) source code for execution by an interpreter,(v) source code for compilation and execution by a just-in-timecompiler, etc. As examples only, source code may be written using syntaxfrom languages including C, C++, C#, Objective C, Haskell, Go, SQL, R,Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5,Ada, ASP (active server pages), PHP, Scala, Eiffel, Smalltalk, Erlang,Ruby, Flash®, Visual Basic®, Lua, and Python®.

None of the elements recited in the claims are intended to be ameans-plus-function element within the meaning of 35 U.S.C. §112(f)unless an element is expressly recited using the phrase “means for,” orin the case of a method claim using the phrases “operation for” or “stepfor.”

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1-8. (canceled)
 9. A control system comprising: a thermostat providing afirst signal in response to detecting a first demand for changing anindoor temperature by a first amount and a second signal in response todetecting a second demand for changing the indoor temperature by asecond amount; a compressor operable at a first capacity and a secondcapacity that is greater than the first capacity; an indoor fan operableat a first speed and a second speed that is greater than the firstspeed; and a controller operating the compressor and the fan: inresponse to the thermostat asserting the first signal, initially at thefirst capacity and the first speed and subsequently at the secondcapacity and the first speed; then in response to the thermostatasserting the second signal, at the second capacity and the secondspeed; and then in response to the thermostat de-asserting the secondsignal, at the second capacity and the first speed until the firstsignal is de-asserted.
 10. The control system of claim 9 wherein: thethermostat detects the first demand when the indoor temperature differsfrom a desired temperature setting of the thermostat by the firstamount; and the thermostat detects the second demand when the indoortemperature differs from the desired temperature setting of thethermostat by the second amount.
 11. The control system of claim 9wherein the controller operates the compressor and the fan, in responseto the thermostat asserting the first signal, initially at the firstcapacity and the first speed for a predetermined time period andsubsequently at the second capacity and the first speed based on anoutdoor air temperature or other measured indicator of outdoor thermalload.
 12. The control system of claim 9 wherein the thermostat assertsthe second signal in response to the indoor temperature differing from adesired temperature by greater than or equal to a predetermined amountafter the compressor and the indoor fan have been operated respectivelyat the second capacity and the first speed for a predetermined timeperiod.
 13. The control system of claim 9 wherein the thermostat assertsthe second signal after the compressor and the indoor fan have beenoperated respectively at the second capacity and the first speed for apredetermined time period.
 14. The control system of claim 9 wherein thethermostat asserts the second signal for a predetermined time period andde-asserts the second signal after the predetermined time period. 15.The control system of claim 9 wherein the thermostat asserts the secondsignal until the indoor temperature differs from a desired temperatureby less than or equal to a predetermined amount and de-asserts thesecond signal after the indoor temperature differs from the desiredtemperature by less than or equal to the predetermined amount.
 16. Thecontrol system of claim 9 wherein the controller turns off thecompressor and the fan after the first signal is de-asserted. 17-23.(canceled)
 24. A system comprising: a compressor operable at a firstcapacity and a second capacity that is greater than the first capacity;an indoor fan operable at a first speed and a second speed that isgreater than the first speed; a thermostat providing a first signal forchanging an indoor temperature by a first amount and a second signal forchanging the indoor temperature by a second amount; and a controlleroperating the compressor and the fan: at the second capacity and thesecond speed in response to the thermostat asserting the second signalAJV[1], and subsequently at the second capacity and the first speed inresponse to the thermostat de-asserting the second signal and assertingthe first signal.
 25. The system of claim 24 wherein the controlleroperates the compressor and the fan at the second capacity and the firstspeed until the first signal is de-asserted and turns off the compressorand the fan after the first signal is de-asserted.
 26. The system ofclaim 24 wherein the controller operates the compressor and the fan atthe second capacity and the first speed based on an outdoor airtemperature or other measured indicator of outdoor thermal load.
 27. Amethod for a compressor operable at a first capacity and a secondcapacity that is greater than the first capacity and an indoor fanoperable at a first speed and a second speed that is greater than thefirst speed, the method comprising: providing a first signal in responseto detecting a first demand for changing an indoor temperature by afirst amount and a second signal in response to detecting a seconddemand for changing the indoor temperature by a second amount; inresponse to the first signal being asserted, operating the compressorand the fan initially at the first capacity and the first speed andsubsequently at the second capacity and the first speed; then inresponse to the second signal being asserted, operating the compressorand the fan at the second capacity and the second speed; and then inresponse to the second signal being de-asserted, operating thecompressor and the fan at the second capacity and the first speed untilthe first signal is de-asserted.
 28. The method of claim 27 furthercomprising operating the compressor and the fan, in response to thefirst signal being asserted, initially at the first capacity and thefirst speed for a predetermined time period and subsequently at thesecond capacity and the first speed based on an outdoor air temperatureor other measured indicator of outdoor thermal load.
 29. The method ofclaim 27 further comprising asserting the second signal in response tothe indoor temperature differing from a desired temperature by greaterthan or equal to a predetermined amount after the compressor and theindoor fan have been operated respectively at the second capacity andthe first speed for a predetermined time period.
 30. The method of claim27 further comprising asserting the second signal after the compressorand the indoor fan have been operated respectively at the secondcapacity and the first speed for a predetermined time period.
 31. Themethod of claim 27 further comprising asserting the second signal for apredetermined time period and de-asserting the second signal after thepredetermined time period.
 32. The method of claim 27 furthercomprising: asserting the second signal until the indoor temperaturediffers from a desired temperature by less than or equal to apredetermined amount; and de-asserting the second signal after theindoor temperature differs from the desired temperature by less than orequal to the predetermined amount.
 33. The method of claim 27 furthercomprising turning off the compressor and the fan after the first signalis de-asserted.
 34. A method for a compressor operable at a firstcapacity and a second capacity that is greater than the first capacityand an indoor fan operable at a first speed and a second speed that isgreater than the first speed, the method comprising: providing a firstsignal for changing an indoor temperature by a first amount and a secondsignal for changing the indoor temperature by a second amount; operatingthe compressor and the fan at the second capacity and the second speedin response to the second signal being asserted; and subsequentlyoperating the compressor and the fan at the second capacity and thefirst speed in response to the second signal being de-asserting and thefirst signal being asserted.
 35. The method of claim 34 furthercomprising: operating the compressor and the fan at the second capacityand the first speed until the first signal is de-asserted; and turningoff the compressor and the fan after the first signal is de-asserted.36. The method of claim 34 further comprising operating the compressorand the fan at the second capacity and the first speed based on anoutdoor air temperature or other measured indicator of outdoor thermalload. 37-40. (canceled)